Method and apparatus for autonomous transmission

ABSTRACT

A method and an apparatus for autonomous transmission in an unlicensed band are provided. The method and apparatus comprising: a wireless device receiving a semi-persistent scheduling (SPS) configuration for first uplink transmission, wherein the SPS configuration includes information regarding an SPS window indicating a time section in which the first uplink transmission is allowed; the wireless device receiving on a DL channel downlink control information (DCI) having an uplink grant that instructs second uplink transmission, wherein the uplink grant includes a second hybrid automatic repeat request process identifier (HARQid) for the second uplink transmission; and the wireless device performing the first uplink transmission in the SPS window when it is confirmed that a wireless medium is in an idle state by performing a listen before talk (LBT) in the SPS window, wherein a first HARQid for the first uplink transmission is not the same as the second HARQid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Application No. 17/397,503,filed on Aug. 9, 2021, which is a continuation of U.S. Application No.16/636,614, filed on Feb. 4, 2020, now U.S. Pat. No. 11,115,859, whichis a National Stage application under 35 U.S.C. § 371 of InternationalApplication No. PCT/KR2018/008843, filed on Aug. 3, 2018, which claimsthe benefit of U.S. Provisional Application No. 62/541,102, filed onAug. 4, 2017 and U.S. Provisional Application No. 62/564,273, filed onSep. 28, 2017. The disclosures of the prior applications areincorporated by reference in their entirety.

BACKGROUND Field

The present disclosure relates to wireless communication, and moreparticularly, to a method for autonomous transmission in a wirelesscommunication system, and an apparatus using the method.

Related Art

In 3rd generation partnership project (3GPP), there was an agreement onan overall schedule and concept for 5G standardization in a workshopheld in September 2015. An enhanced mobile broadband (eMBB), massivemachine type communication (MTC), ultra-reliable and low latencycommunication (URLLC), or the like was specified as a top-leveluse-case. In order to satisfy a service scenario and a new requirement,in the 3GPP, it was determined to define a new radio (NR) different fromthe existing long term evolution (LTE), and both the LTE and the NR weredefined as a 5G radio access technique.

In general, in uplink (UL) transmission, a UL resource is firstallocated by a base station (BS) and then a user equipment (UE)transmits data on the basis of the allocated resource. This is calleddynamic UL transmission since the UL resource is dynamically allocated.When the UL resource is pre-configured and then transmission isperformed periodically or aperiodically based on the configured ULresource, this is called autonomous UL transmission or semi-persistentscheduling (SPS) UL transmission. The autonomous UL transmission may beparticularly useful in an unlicensed band which is shared by variouscommunication protocols and thus makes it difficult to determine when awireless medium will be idle.

A hybrid automatic repeat request (HARQ) is also introduced in theunlicensed band to increase reliability of communication. In general,the UE may operate a plurality of HARQ processes simultaneously. Thereis a need for a method capable of operating the HARQ processes without acollision in a situation where dynamic UL transmission and autonomous ULtransmission co-exist.

SUMMARY

The present disclosure provides a method for autonomous transmission inan unlicensed band and a device using the same.

In an aspect, a method for autonomous transmission in an unlicensed bandis provided. The method includes receiving, by a wireless device, asemi-persistent scheduling (SPS) configuration for first uplinktransmission, wherein the SPS configuration comprises informationregarding an SPS window indicating a time region in which the firstuplink transmission is allowed, receiving, by the wireless device,downlink control information (DCI) having an uplink grant whichindicates second uplink transmission on a downlink (DL) channel, whereinthe uplink grant comprises a second hybrid automatic repeat requestprocess identifier (HARQid) for the second uplink transmission, andperforming, by the wireless device, the first uplink transmission in theSPS window upon confirming that a wireless medium is idle by performinga listen before talk (LBT) in the SPS window, wherein a first HARQid forthe first uplink transmission is not the same as the second HARQid.

In another aspect, a device for autonomous transmission in an unlicensedband includes a transceiver configured to transmit and receive a radiosignal, and a processor operatively coupled to the transceiver. Theprocessor is configured to control the transceiver to receive asemi-persistent scheduling (SPS) configuration for first uplinktransmission, wherein the SPS configuration comprises informationregarding an SPS window indicating a time region in which the firstuplink transmission is allowed, control the transceiver to receivedownlink control information (DCI) having an uplink grant whichindicates second uplink transmission on a downlink (DL) channel, whereinthe uplink grant comprises a second hybrid automatic repeat requestprocess identifier (HARQid) for the second uplink transmission, andcontrol the transceiver to perform the first uplink transmission in theSPS window upon confirming that a wireless medium is idle by performinga listen before talk (LBT) in the SPS window, wherein a first HARQid forthe first uplink transmission is not the same as the second HARQid.

A collision of HARQ processes can be avoided in a situation wheredynamic UL transmission and autonomous UL transmission co-exist.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a radio frame structure to which the presentdisclosure is applied.

FIG. 2 shows an example of a UL HARQ operation based on dynamicscheduling.

FIG. 3 shows an example of a UL HARQ operation based on semi-persistentscheduling (SPS).

FIG. 4 shows an example of an SPS window.

FIG. 5 shows an example of HARQ retransmission for SPS.

FIG. 6 shows an example of a collision occurring when an HARQid havingthe same SPS as dynamic scheduling is allocated.

FIG. 7 is a block diagram showing a wireless communication system forwhich an embodiment of the present disclosure is implemented.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Technical features described hereinafter may be applied in acommunication specification by the 3rd Generation Partnership Project(3GPP) standardization organization or a communication specification bythe Institute of Electrical and Electronics Engineers (IEEE)standardization organization. For example, the communicationspecification by the 3GPP standardization organization includes a LongTerm Evolution (LTE) and/or an evolution of the LTE system. Theevolution of the LTE system includes LTE-A (Advanced), LTE-A Pro, and/or5G New Radio (NR). The communication specification by the IEEEstandardization organization includes a wireless local area networksystem such as IEEE 802.11a/b/g/b/ac/ax. The above-described system usesvarious multiple access technologies such as Orthogonal FrequencyDivision Multiple Access (OFDMA) and/or Single Carrier-FrequencyDivision Multiple Access (SC-FDMA) for an uplink and/or a downlink. Forexample, only OFDMA may be used for a downlink, only SC-FDMA may be usedfor an uplink, and OFDMA and SC-FDMA may be used with mixed for adownlink and/or an uplink.

A wireless device may be fixed or mobile, and may be referred to asother terms such as a user equipment (UE), a mobile station (MS), amobile terminal (MT), a user terminal (UT), a subscriber station (SS), apersonal digital assistant (PDA), a wireless modem, a handheld device,etc. The wireless device may also be a device that supports only datacommunication such as a Machine-Type Communication (MTC) device.

A base station (BS) generally refers to as a fixed station thatcommunicates with the wireless device and may be referred to as otherterms such as an evolved-NodeB (eNB), a gNB, a base transceiver system(BTS), an access point, etc. A Transmission Reception Point (TRP)includes an antenna array having one or more antenna elements. The BSmay include one or more TRPs.

New radio (NR), which is 5G radio access technology supports variousbandwidths and frequency bands for more flexible scheduling. NR alsosupports frequency bands of 6 GHz or above as well as frequency bands of6 GHz or below. Supported bandwidths are maximum 100 MHz at frequenciesof 6 GHz or below and maximum 400 MHz at frequencies of 6 GHz or above.Further, unlike 3GPP LTE fixed to subcarrier spacing of 15 kHz, NR maysupport various subcarrier spacing of 15 kHz, 30 kHz, 60 kHz, 120 kHz,and 240 kHz.

An NR specification supports various numerologies. A structure of aradio frame is changed according to numerology. Table 1 represents anexample of supported numerology.

Table 1 Numerology index (µ) Subcarrier spacing (kHz) Cyclic prefixNumber of OFDM symbols per slot Number of slots per radio frame Numberof slots per subframe 0 15 Normal 14 10 1 1 30 Normal 14 20 2 2 60Normal 14 40 4 2 60 Extended 12 40 4 3 120 Normal 14 80 8 4 250 Normal14 160 16

FIG. 1 illustrates an example of a radio frame structure to which thepresent dusclosure is applied. This illustrates an example with anumerology index µ = 0 of Table 1.

A slot may include a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols. The number of OFDM symbols in slots ofTable 1 is only an example. The OFDM symbol is only for representing onesymbol period in a time domain and does not limit a multiple accessscheme or a term. For example, the OFDM symbol may be referred to asanother term such as a single carrier-frequency division multiple access(SC-FDMA) symbol, a symbol period, etc.

OFDM symbols in the slot may be classified into a downlink (DL),flexible, and an uplink (UL). The classification is referred to as aslot format. A base station may notify a wireless device of informationabout the slot format. The wireless device may receive information onthe slot format through an upper layer signal and/or downlink controlinformation (DCI) on a Physical Downlink Control Channel (PDCCH). Thewireless device assumes that DL transmission occurs in a DL OFDM symbolor a flexible OFDM symbol. The wireless device performs UL transmissionin a UL OFDM symbol or a flexible OFDM symbol. A format of a slot may bedetermined based on which OFDM symbol within a slot is D, X or U.

A resource block (RB) includes a plurality of continuous subcarriers ina frequency domain. For example, the RB may include 12 subcarriers. Thecommon RB (CRB) is an RB in which an index is determined according tonumerology. A Physical RB (PRB) is an RB defined in a bandwidth part(BWP). It is assumed that a total bandwidth of a particular numerologyis 20 RB. The CRB is indexed from 0 to 19. When the BWP includes fourCRBs (CRB 4 to CRB 7) among the 20 RBs, the PRB in the BWP are indexedfrom 0 to 3.

The BWP may be defined through a starting offset and a size from a CRB 0on a given carrier. A specific number (e.g., maximum four) of BWP may beconfigured to the wireless device. At a particular time point, only aparticular number (e.g., one) of BWPs per cell may be activated. Thenumber of configurable BWPs or the number of activated BWPs may be setin common to an UL and a DL or individually set. The wireless device mayexpect DL transmission only in the activated DL BWP. The wireless devicemay perform UL transmission only in the activated UL BWP.

The wireless device may perform cell search to obtain time and/orfrequency synchronization with the cell and to obtain a cell ID. Forcell search, synchronization channels such as a Primary SynchronizationSignal (PSS), a Secondary Synchronization Signal (SSS), and a PhysicalBroadcast CHannel (PBCH) may be used.

The following embodiments may be operated in a licensed band or anunlicensed band. The licensed band is a band that guarantees exclusiveuse of a particular communication protocol or a particular serviceprovider. The unlicensed band is a band in which various communicationprotocols coexist and that guarantees shared use. For example, theunlicensed band may include 2.4 GHz band and/or 5 GHz band used by awireless local area network (WLAN). In the unlicensed band, it isassumed that a channel is occupied through contention between respectivecommunication nodes. Therefore, in communication in the unlicensed band,it is required to confirm that signal transmission is not achieved byother communication nodes by performing channel sensing. This isreferred to as listen before talk (LBT) or clear channel assessment(CCA) for convenience. When it is determined that the othercommunication node does not transmit any signal in a particular channel,it is referred to that ‘a channel is idle’, ‘CCA was confirmed’, ‘or LBTwas confirmed’. Wen it is said that ‘Perform LBT’, ‘Perform CCA’, or‘Perform carrier sense (CS)’, it implies that whether a channel is idleor is used by another node is confirmed first and thereafter the channelis accessed. A cell operating in the unlicensed band is referred to asan unlicensed cell or Licensed-Assisted Access (LAA) cell. A celloperating in the licensed band is referred to as a licensed cell.

The DL channel includes a Physical Downlink Control Channel (PDCCH), aPhysical Downlink Shared Channel (PDSCH) and a Physical BroadcastChannel (PBCH). The UL channel includes a Physical Uplink ControlChannel (PUCCH), a Physical Uplink Shared Channel (PUSCH) and a PhysicalRandom Access Channel (PRACH).

The PDSCH carries DL data. The PBCH carries a Master Information Block(MIB) necessary for initial access. The PUSCH carries UL data.

The PDCCH carries DCI. The DCI includes a UL grant having resourceallocation that schedules PUSCH transmission or a DL grant havingresource allocation that schedules PDSCH transmission. A controlresource set (CORESET) is defined as a resource for monitoring thePDCCH. A unique identifier is masked to cyclic redundancy check (CRC) ofthe DCI so that the wireless device may identify an owner or content ofDCI in the PDCCH. The identifier is referred to as a Radio NetworkTemporary Identifier (RNTI). When the DCI includes UL grant or DL grantfor a particular wireless device, Cell-RNTI (C-RNTI) is used. When theDCI carries system information, system information-RNTI (SI-RNTI) isused.

The PUCCH carries uplink control information (UCI). The UCI may includehybrid automatic repeat request (HARQ) ACK/NACK and/or channel stateinformation (CSI). The PUCCH may be transmitted in one or more OFDMsymbols according to a PUCCH format.

FIG. 2 shows an example of a UL HARQ operation based on dynamicscheduling. In dynamic UL scheduling, a BS uses a PDCCH to dynamicallyallocate a UL resource to a wireless device.

The wireless device receives a PDCCH 210 having an initial UL grant. Theinitial UL grant includes information regarding a start point and lengthfor transmitting a PUSCH 220. The start point may be indicated by usinga slot at which transmission of the PUSCH 220 starts and an index of anOFDM symbol within the slot. The length indicates the number of OFDMsymbols on which the PUSCH 220 is transmitted. The initial UL grant mayfurther include an HARQ process identifier (HARQid) which identifies anHARQ process.

The wireless device transmits the PUSCH 220 having a UL transmissionblock on the basis of the initial UL grant.

The wireless device receives a PDCCH 230 having a retransmission ULgrant. The retransmission UL grant may include information regarding astart point and length for transmitting a PUSCH 240 for retransmission,and the HARQid.

The wireless device transmits the PUSCH 240 having a retransmissionblock on the basis of the retransmission UL grant.

A BS schedules UL transmission and retransmission by using PDCCHtransmission. A PDCCH-to-PUSCH transmission timing may be flexiblyadjusted, instead of being fixed.

For buffer management, the number of HARQ processes that can beconfigured per cell is predetermined for the wireless device. Themaximum number of HARQ processes for a PDSCH and the maximum number ofHARQ processes for a PUSCH may be given separately. The maximum numberof HARQ processes may be fixed to a specific value (e.g., 8 or 16), ormay be configured by the BS.

FIG. 3 shows an example of a UL HARQ operation based on semi-persistentscheduling (SPS). In the SPS, a wireless device performs UL transmissionbased on UL resources given in advance. The UE resources may be givenaccording to a buffer status for UL data.

The wireless device receives an SPS configuration 310 from a BS. The SPSconfiguration 310 may be received through a PDCCH or a radio resourcecontrol (RRC) message. The SPS configuration 320 may include one or moreUL resource sets required for UL transmission. Each UL resource set mayinclude at least one of an SPS window, HARQ information, frequencyallocation for a PUSCH and transmit power command (TPC) for the PUSCH.

The wireless device may receive SPS DCI 320 from the BS. The SPS DCI 320may instruct a start or stop of SPS transmission. The SPS DCI 320 mayinclude information indicating a time at which SPS transmission startsand/or a time at which SPS transmission stops. A dedicated RNTI (e.g.,SPS RNTI) may be masked to a PDCCH for carrying the SPS DCI 320. Ifadditional start/stop is not necessary, reception of the SPS DCI 320 maynot be required.

The wireless device may transmit UL data 330 on the PUSCH in an SPSwindow.

If retransmission is required, the BS may transmit retransmission DCI340 to the wireless device on the PDCCH. The retransmission DCI 340 isused in PUSCH scheduling for retransmission. A dedicated RNTI (e.g., SPSC-RNTI) may be masked to the PDCCH for carrying the transmission DCI340.

FIG. 4 shows an example of an SPS window.

The SPS window is a duration in which a wireless device is allowed toperform UL transmission. In the presence of UL data to be transmitted,the wireless device may transmit a PUSCH in each SPS window.

The SPS window may include one or more subframes (SFs). The SPS windowmay include a plurality of consecutive SFs. The SPS window may appearperiodically, and this periodicity is called an SPS window period.

Information regarding the SPS window may be included in an SPSconfiguration or SPS DCI. SPS window information may include a startingSF at which the SPS window starts, an SPS window period, and the numberof SFs included in the SPS window.

Although the SF is used as a unit of configuring the SPS window inembodiments described below, this is for exemplary purposes only. TheSPS window may be represented in a slot, OFDM symbol, or a schedulinginterval. In case of the slot unit, the SPS window may include one ormore slots.

Although the term ‘SPS transmission’ is used for convenience, this isfor exemplary purposes only. This may be called ‘autonomoustransmission’ since UL transmission is autonomously performed based on apre-configured resource. The SPS window for UL transmission may becalled an autonomous uplink (AUL) window.

Now, a UL HARQ operation of a wireless device is described in anunlicensed band in which SPS transmission and dynamic schedulingtransmission co-exist.

The wireless device obtains a time t1 at which CCA succeeds within anSPS window and a last time t2 of an SF to which the time t1 belongs. Ifa value of t2-t1 is greater than a first threshold, the wireless devicemay transmit a PUSCH. If a code rate of the PUSCH is less than a secondthreshold (e.g., if the code rate is less than ⅔), the wireless devicemay transmit the PUSCH. For example, assume that the first thresholdcorresponds to 4 OFDM symbols, and one SF includes 14 OFDM symbols. Ift1 corresponds to a 7^(th) OFDM symbol, the wireless device may transmitthe PUSCH in the SF. Information on the first threshold and secondthreshold may be reported by a BS to the wireless device.

Assume that an SF in which LBT succeeds within the SPS window is calledan initiating SF. The wireless device may transmit the PUSCH withoutadditional LBT during a maximum channel occupation time (MCOT) which isleft until the end of a next SF from the initiating SF within the SPSwindow. Even if the MCOT is left, the PUSCH may be transmitted onlyuntil the next SF. The MCOT implies a time (or the number of SFs) inwhich continuous transmission is possible without additional LBT afterthe wireless device confirms that a channel is idle through an LBToperation.

A reference HARQid (RHARQid) may be defined in each SPS window. TheRHARQid may be an HARQid applied to a first SF of the SPS window.Alternatively, the RHARQid may be an HARQid applied to a first SF inwhich the PUSCH is transmitted.

An increase/decrease of the HARQid may imply an increase/decrease of anHARQid value itself. When a set including one or more HARQids applied toSPS transmission is defined and HARQid(i) denotes an HARQidcorresponding to an i-th element in the set, the increase/decrease ofthe HARQid may imply a corresponding HARQid depending on anincrease/decrease of i. An increase/decrease offset of the HARQid mayimply an increase/decrease offset of i. A minimum/maximum HARQid valuemay imply an HARQid value corresponding to a first/last element in theset.

Assume that the SPS window includes N SFs, and an SPS window period isP. Herein, N>= 1, P>=I, where N and P are integers. When the wirelessdevice can transmit the PUSCH only in one SF within each SPS window, theHARQid for PUSCH transmission may be defined as follows.

In an embodiment, the RHARQid may be commonly applied regardless ofwhich SF within the SPS window is used by the wireless device totransmit the PUSCH. If RHARQid=0 in the SPS window, HARQid=0 may beapplied for all SFs within the SPS window.

In another embodiment, the RHARQid is applied to the first SF of the SPSwindow, and the HARQid which sequentially increases from the RHARQid isapplied from a next SF. For example, if N=4 and if RHARQid=0 in the SPSwindow, HARQid=0, 1, 2, 3 may be applied respectively to four SFs withinthe SPS window.

Assume that the SPS window includes N SFs, and an SPS window period isP. Herein, N>=1, P>=1, where N and P are integers. When the wirelessdevice can transmit the PUSCH in up to M SFs (M>=1 where M is aninteger) within each SPS window, the HARQid for PUSCH transmission maybe defined as follows.

In an embodiment, the RHARQid is applied to the first SF of the SPSwindow, and the HARQid which sequentially increases from the RHARQid isapplied from a next SF. For example, if N=4 and if RHARQid=0 in the SPSwindow, HARQid=0, 1, 2, 3 may be applied respectively to four SFs withinthe SPS window.

In another embodiment, the RHARQid is applied to the first SF of the SPSwindow, and the HARQid which repeatedly increases from the RHARQid toRHARQid+M-1 is applied from a next SF. For example, if N=4, M=2 and ifRHARQid=0 in the SPS window, HARQid=0, 1, 0, 1 may be appliedrespectively to four SFs within the SPS window. If N=4, M=2 and ifRHARQid=3 in the SPS window, HARQid=3, 4, 3, 4 may be appliedrespectively to four SFs within the SPS window.

In still another embodiment, the RHARQid is applied to an SF in whichthe PUSCH is actually transmitted within the SPS window, and the HARQidwhich repeatedly increases from the RHARQid to RHARQid+M-1 is appliedfrom a next SF. For example, if N=4, M=2 and RHARQid=0, when the PUSCHis transmitted for 2 SFs from a 2^(nd) SF in the SPS window, HARQid=0, 1may be applied respectively to PUSCH transmission of the 2^(nd) SF and a3^(rd) SF.

In the above schemes, if the HARQid increases to reach a maximum HARQidthat can be used in the SPS window, allocation may start again from aminimum HARQid.

Now, a method of determining RHARQid is described.

Assume that the SPS window includes N SFs, and an SPS window period isP. Herein, N>=1, P>=1, where N and P are integers. When the wirelessdevice can transmit the PUSCH in up to M SFs (M>=1 where M is aninteger) within each SPS window, the RHARQid for each SPS window may bedefined as follows.

(Scheme 1) A common RHARQid may be applied for all SPS windows. Forexample, RHARQid=0 may be applied for all SPS windows. A wireless devicemay receive information on the RHARQid through an RRC message or SPSDCI.

(Scheme 2) An RHARQid may increase sequentially under the constraint ofthe maximum number of HARQ processes. For example, if the maximum numberof HARQ processes is 4, the RHARQid may be allocated in order of 0, 1,2, 3, 0, 1, 2, 3 for 8 consecutive SPS windows.

(Scheme 3) An RHARQid may sequentially increase according to an HARQidreuse cycle. The RHARQid is reset every HARQid reuse cycle. For example,if an SPS window period is 6 SFs and if the HARQid reuse cycle is 18,there are three SPS windows within the HARQid reuse cycle. The RHARQidmay be allocated in order of 0, 1, 2 for the three SPS windows withinthe HARQid reuse cycle.

(Scheme 4) A combination of the scheme 2 and the scheme 3 may beapplied. If the number of SPS windows within an HARQid reuse cycle isgreater than the maximum number of HARQ processes, an RHARQid increasesnot to exceed the maximum number of HARQ processes. If the number of SPSwindows within the HARQid reuse cycle is less than the maximum number ofHARQ processes, the RHARQid increases based on the HARQid reuse cycle.

(Scheme 5) A next HARQid of an HARQid applied to a last SF of a previousSPS window may be an RHARQid of a next SPS window. For example, if N=4,M=3 and if the maximum number of HARQ processes is 6, HARQids withinfour SPS windows are {0, 1, 2, 0}, {1, 2, 3, 1}, {2, 3, 4, 2}, {3, 4, 5,3}. If N=4, M=4 and if the maximum number of HARQ processes is 6, theHARQids within four SPS windows are {0, 1, 2, 3}, {4, 5, 0, 1 }, {2, 3,4, 5}, {0, 1, 2, 3}.

In the above schemes 1 to 5, an increase interval by which the RHARQidincreases according to the SPS window may be defined as follows.

-   The increase interval of the RHARQid may be 1.-   When different HARQids are applied to different SFs in the SPS    window, the increase interval of the RHARQid may be the number N of    SFs included in the SPS window.-   When up to M different HARQids are applied within the SPS window,    the increase interval of the RHARQid may be the maximum number M of    SFs in which the wireless device can transmit the PUSCH within the    SPS window.

Now, an example of applying the proposed scheme is described. Assumethat N=4, M=3, the maximum number of HARQ processes is 6, and an HARQidranges from 0 to 5. A number inside { } implies an HARQid allocated toSFs within each SPS window.

(Example 1) {0, 1, 2, 3}, {4, 5, 0, 1}, {2, 3, 4, 5}, {0, 1, 2, 3},...., when an increase interval of an RHARQid is N. This scheme may beunderstood as a scheme in which an HARQid in an HARQid set allocated toSPS transmission is allocated by being increased for each SF within theSPS window. This scheme may also be understood as a scheme in which anHARQid of a first SF of a current SPS window is allocated based on anHARQid of a last SF of a previous SPS window.

(Example 2) {0, 1, 2, 0}, {3, 4, 5, 3}, {0, 1, 2, 0}, {3, 4, 5, 3}, ...,when the increase interval of the RHARQid is M, and an HARQid in SPSincreases to up to RHARQid+M-1.

(Example 3) {0, 1, 2, 3}, {3, 4, 5, 0}, {0, 1, 2, 3}, {3, 4, 5, 0}, ...,when the increase interval of the RHARQid is M, and the HARQid in theSPS increases to up to RHARQid+N-1.

(Example 4) The increase interval of the HARQid may be 1, and the HARQidin the SPS may increase to up to RHARQid+N-1. This scheme may beunderstood as a scheme in which an HARQid to be allocated to a first SFbetween adjacent SPS windows is changed when the maximum number of HARQprocesses allocated to the SPS is less than M. For example, {0, 1, 2,0}, { 1, 2, 0, 1}, {2, 0, 1, 2}, {0, 1, 2, 0}, ..., when M=3, N=4, andwhen the maximum number of HARQ processes allocated to the SPS is 3(HARQid:0~2).

FIG. 5 shows an example of HARQ retransmission for SPS.

Assume that a common HARQid=x is applied for an SPS window 1 and an SPSwindow 2. A wireless device transmits first initial UL data on a firstPUSCH, with HARQid=x in the SPS window 1. The wireless device transmitssecond initial UL data on a second PUSCH, with HARQid=x in the SPSwindow 2.

The wireless device receives retransmission DCI 510 after the SPS window2. The retransmission DCI 510 includes information on an HARQid forretransmission. If the retransmission DCI 510 indicates HARQid=x,whether retransmission instructed by the wireless device is for PUSCHtransmission of the window 1 or PUSCH transmission of the window 2 maybe ambiguous. To solve this problem, the following schemes are proposed.

In an embodiment, an HARQid of a PUSCH transmitted in the SPS window maynot be valid from a time at which the SPS window including the sameHARQid appears at a later time. Alternatively, the HARQid of the PUSCHtransmitted in the SPS window may not be valid from a time after aspecific timing offset. If the HARQid is not valid, the wireless devicedoes not perform HARQ retransmission, or does not expect retransmissionDCI.

Even if the PUSCH is transmitted in a specific SPS window, HARQ for thePUSCH may not be valid after a specific time is over. The HARQ for thePUSCH may not be valid from a time at which a next SPS window appearsafter the PUSCH is transmitted in the specific SPS window. After thePUSCH is transmitted in the specific SPS window, the HARQ for the PUSCHmay not be valid from a time after a timing offset.

In another embodiment, upon receiving retransmission DCI for the HARQidallocated to the SPS window, the wireless device may regard that the DCIindicates retransmission of a PUSCH transmitted most recently with thesame HARQid. In the example of FIG. 5 , the wireless device may regardthat the retransmission DCI 510 indicates retransmission for the PUSCHof the SPS window 2. This scheme may be useful if a BS can reliablydetermine whether the wireless device has transmitted the PUSCH in theSPS window.

In still another embodiment, retransmission DCI may include windowinformation regarding an SPS window in which the PUSCH requiringretransmission is transmitted. The window information may indicate afirst SPS window or second SPS window which appears at a transmissiontime of retransmission DCI or before a timing offset for thetransmission time of retransmission DCI (at the same time, whichincludes the same HARQid as the HARQid indicated by retransmission DCI).

The window information in the retransmission DCI may be implemented asfollows.

-   The window information is included in the retransmission DCI as an    independent field.-   The window information is indicated as a scrambling sequence or CRC    mask sequence of retransmission DCI.-   The window information may be indicated by reusing another field in    the retransmission DCI. For example, the window information may be    indicated by using a field fixed to a specific value in the existing    SPS DCI such as UL TPC, DM RS cyclic shift/OCC, MCS or the like. The    window information may be indicated by using a field which is not    used in SPS DCI such as an HARQ process number, a 2-stage PUSCH    grant (PUSCH trigger type A, PUSCH trigger type B, etc.).

The window information may be indicated together with informationindicating that retransmission DCI is to be scheduled for SPS PUSCHinitial transmission or retransmission. For example, a 2-bit field mayindicate ‘SPS PUSCH initial transmission’, ‘retransmission for first SPSwindow before retransmission DCI’, ‘retransmission for second SPS windowbefore retransmission DCI’, and ‘retransmission for third SPS windowbefore retransmission DCI’.

The wireless device may not transmit the PUSCH with the same HARQid inthe SPS window indicated by the retransmission DCI. Alternatively, evenif the wireless device transmits the PUSCH, there may be a mismatchbetween scheduling indicated by the retransmission DCI and PUSCHtransmission. The wireless device may inform the BS of the above errorthrough PUSCH transmission. More specifically, the wireless device mayinform the BS of the above error by transmitting only a buffer statusreport (BSR) on the PUSCH scheduled by the retransmission DCI.

The window information may be included in the PUSCH for SPSretransmission to report a specific SPS window of which retransmissioncorresponds to a retransmission PUSCH. Window information may beinserted in a form of uplink control information (UCI) in part of atransmission region for PUSCH data. The window information may berepresented as a DM-RS transmitted together with the PUSCH, anorthogonal cover code (OCC) for the DM-RS, a scrambling sequence of thePUSCH, or a masking sequence of CRC for PUSCH data.

A plurality of SPS configurations may be given to each wireless device.The aforementioned HARQid allocation scheme may be commonly applied forthe plurality of SPS configurations. Alternatively, the aforementionedHARQid allocation scheme may be individually applied for every SPSwindow of each SPS configuration.

FIG. 6 shows an example of a collision occurring when an HARQid havingthe same SPS as dynamic scheduling is allocated.

An HARQid pre-allocated to an SPS window may be applied to SPStransmission and retransmission. When many HARQids are allocated to theSPS window, the number of HARQids that can be used in HARQ for dynamicscheduling is decreased, which may result in a decrease in a freedom ofdegree of dynamic scheduling. However, ambiguity may occur when the sameHARQid is applied to both SPS transmission and dynamic schedulingtransmission. The following schemes are proposed to avoid the collisionof the HARQid.

In an embodiment, upon receiving DCI for dynamic scheduling to which theHARQid allocated to the SPS window is applied within k SFs before theSPS window, a wireless device may perform PUSCH transmission based ondynamic scheduling and may not perform SPS transmission for the HARQidin the SPS window. Herein, k>=0, where K is an integer. Upon receivingDCI for dynamic scheduling to which the HARQid allocated to the SPSwindow is applied before the SPS window, the wireless device may performPUSCH transmission based on dynamic scheduling and may not perform SPStransmission for the HARQid in the SPS window. Upon receiving DCI fordynamic scheduling with HARQid=x, the wireless device may not performSPS transmission with HARQid=x until HARQ based on the DCI is complete.

In another embodiment, even upon receiving DCI for dynamic scheduling towhich the HARQid allocated to the SPS window is applied later than y SFsbefore the SPS window, the wireless device may perform SPS transmissionof the HARQid in the SPS window. Herein, y>=l, where y is an integer.

In another embodiment, upon receiving DCI for SPS configuration and SPStransmission with HARQid=x after receiving DCI for dynamic schedulingwith HARQid=x, the wireless device may ignore DCI for dynamic schedulingand perform SPS transmission.

In still another embodiment, the DCI for dynamic scheduling may includea value of a validity timer indicating a valid time of UL scheduling.While the validity timer is running, the wireless device may not performSPS transmission with the same HARQid as the HARQid of the DCI fordynamic scheduling.

In still another embodiment, upon decoding DCI transmitted by a BS toindicate retransmission (or initial transmission) for HARQid=x within aspecific time after the wireless device performs SPS transmission withHARQid=x, scheduling based on the DCI may be ignored. This may beapplied particularly to a case where SPS transmission corresponds toinitial transmission.

The aforementioned embodiments may be applied to a scheme in which theHARQid is pre-allocated to the SPS window or in which the wirelessdevice can transmit a PUSCH by randomly selecting the HARQid.

The wireless device may randomly select and use the HARQid in SPStransmission. Not only initial transmission but also retransmission maybe performed on a PUSCH in a specific SF within the SPS window. In thiscase, the wireless device may transmit additional transmission togetherwith initial/retransmission UL data on the PUSCH. The additionalinformation may include at least any one of an identifier of thewireless device, an HARQid, a redundancy version (RV), a new dataindicator (NDI), and the number of SFs in which the PUSCH istransmitted.

When the wireless device transmits a plurality of PUSCHs in a pluralityof consecutive SPS SFs, the following scheme may be applied.

(Scheme1) An ID of the wireless device is transmitted in first Q SFs(Q>=1 where Q is an integer), the ID of the wireless device is nottransmitted on a PUSCH transmitted in the remaining SFs. A BS mayrecognize that the PUSCH received in the remaining SFs is transmitted bythe same wireless device.

The BS may omit PUSCH reception in a first SF. The ID of the wirelessdevice may be transmitted in the last W SFs (W>=1 where W is aninteger), and the ID of the wireless device may not be transmitted on aPUSCH transmitted in the remaining SFs.

(Scheme 2) An HARQid is transmitted in a first SF, and the HARQid is nottransmitted in the remaining SFs. A BS may obtain an HARQid of a PUSCHtransmitted through consecutive SFs on the basis of the HARQid of thePUSCH transmitted in the first SF. For example, it may be assumed thatthe HARQid increases to a specific value (e.g., 1) for every next SF.Considering that the BS may omit PUSCH reception in the first SF, theHARQid may be transmitted in the last SF, and the HARQid may not betransmitted in the remaining SFs.

(Scheme 3) An RV is transmitted in a first SF, and the RV is nottransmitted in the remaining SFs. A BS and a wireless device may assumethat an RV of a PUSCH transmitted through the remaining consecutive SFsis the same as an RV of a PUSCH transmitted in the first SF. Consideringthat the BS may omit PUSCH reception in the first SF, the RV may betransmitted in a last SF, and the RV may not be transmitted in theremaining SFs.

(Scheme 4) The number of SFs in which a PUSCH is transmitted in a firstSF may be reported. A wireless device may transmit the number of SFs inwhich the PUSCH will be transmitted in the first SF (or a last SF or allSFs) in which the PUSCH is transmitted.

An SF in which the additional information is transmitted may be limitedto an SF in which the PUSCH is transmitted by using all OFDM symbols oran SF in which the PUSCH is transmitted by using at least a specificnumber (e.g., 13 or 12) of OFDM symbols.

Now, a method of transmitting HARQ ACK for SPS transmission isdescribed.

Regarding SPS transmission, a BS may transmit HARQ ACK for informingwhether reception succeeds on a DL channel. The HARQ ACK may be includedin DCI and transmitted on a PDCCH.

In an embodiment, a wireless device may receive from the BS an RNTI usedfor monitoring the PDCCH carrying the HARQ ACK and/or configurationinformation including an HARQid corresponding to HARQ-ACK. Theconfiguration information may be received through an RRC message.

Assume that the wireless device is configured to perform SPStransmission through N HARQids. A location of a bit field of HARQ-ACKcorresponding to a smallest HARQid among a plurality of HARQ-ACKs in DCImay be included in the configuration information. Regarding theremaining HARQids, the location of the bit field may be determinedsequentially in an ascending order of the HARQid.

If HARQ-ACKs for all HARQids are not included in one DCI, an RNTI foradditional DCI and the location of the bit field of HARQ-ACK in theadditional DCI may be given. A field may also be configured for RV (andNDI) in the same format as an HARQ-ACK feedback. In the abovedescription, the location of the bit field may imply a location in anencoder for joint coding a plurality of HARQ-ACKs (or RV, NDI).

In another embodiment, the wireless device may receive from the BS theconfiguration information including the RNTI used for monitoring thePDCCH carrying the HARQ ACK. The configuration information may bereceived through an RRC message.

DCI may include an HARQid corresponding to the HARQ-ACK. The DCI mayinclude at least one HARQid field and HARQ-ACK corresponding to eachHARQid. If one DCI includes a plurality of HARQ-ACKs for a plurality ofwireless devices, a location of a field to be confirmed by each wirelessdevice in the DCI may be given.

HARQ-ACK may indicate one of three states including ACK or NACK or DTX.ACK indicates successful reception, NACK indicates that reception isachieved with an error, and DTX indicates a reception failure. Inparticular, if RV/NDI is included together in DCI, the DTX state may beexpressed using a specific RV value (e.g., RV not including systematicinformation, RV1) or a specific NDI value (e.g., NDI indicatingretransmission).

If the wireless device receives HARQ ACK in an i-th SF, PUSCHretransmission may be performed after an (i+K)-th SPS SF. K>= 1 where Kis an integer. The value K may be predetermined as K=4, or may be set bythe BS.

FIG. 7 is a block diagram showing a wireless communication system forwhich an embodiment of the present disclosure is implemented.

A wireless device 50 includes a processor 51, a memory 52, and atransceiver 53. The memory 52 is coupled to the processor 51, and storesvarious instructions executed by the processor 51. The transceiver 53 iscoupled to the processor 51, and transmits and/or receives a radiosignal. The processor 51 implements the proposed functions, procedures,and/or methods. In the aforementioned embodiment, an operation of thewireless device may be implemented by the processor 51. When theaforementioned embodiment is implemented with a software instruction,the instruction may be stored in the memory 52, and may be executed bythe processor 51 to perform the aforementioned operation.

A BS 60 includes a processor 61, a memory 62, and a transceiver 63. TheBS 60 may operate in an unlicensed band. The memory 62 is coupled to theprocessor 61, and stores various instructions executed by the processor61. The transceiver 63 is coupled to the processor 61, and transmitsand/or receives a radio signal. The processor 61 implements the proposedfunctions, procedures, and/or methods. In the aforementioned embodiment,an operation of the BS may be implemented by the processor 61.

The processor may include Application-Specific Integrated Circuits(ASICs), other chipsets, logic circuits, and/or data processors. Thememory may include Read-Only Memory (ROM), Random Access Memory (RAM),flash memory, memory cards, storage media and/or other storage devices.The transceiver may include a baseband circuit for processing a radiosignal. When the above-described embodiment is implemented in software,the above-described scheme may be implemented using a module (process orfunction) which performs the above function. The module may be stored inthe memory and executed by the processor. The memory may be disposed tothe processor internally or externally and connected to the processorusing a variety of well-known means.

In the above exemplary systems, although the methods have been describedon the basis of the flowcharts using a series of the steps or blocks,the present invention is not limited to the sequence of the steps, andsome of the steps may be performed at different sequences from theremaining steps or may be performed simultaneously with the remainingsteps. Furthermore, those skilled in the art will understand that thesteps shown in the flowcharts are not exclusive and may include othersteps or one or more steps of the flowcharts may be deleted withoutaffecting the scope of the present invention.

What is claimed is:
 1. A method for uplink (UL) transmission in a wireless communication system, the method performed by a wireless device operating in an unlicensed band and comprising: receiving, from a base station, an UL configuration for configure UL transmission without dynamic UL grant in which the wireless device performs UL transmission in accordance with the UL configuration, the UL configuration including a periodicity for the UL transmission without UL grant and a number of allocated slots in the periodicity; selecting at least one hybrid automatic repeat request process identifier (HARQ-ID) for at least one UL channel to be transmitted according to the UL configuration; perform listen before talk (LBT) to check that the unlicensed band is idle in the allocated slots; and transmitting, to the bases station, the at least one uplink channel in at least one slot of the allocated slots based on the unlicensed band being idle, wherein the at least one uplink channel includes the at least one selected HARQ-ID.
 2. The method according to claim 1, wherein the at least one HARQ-ID for the at least one uplink channel is selected among a plurality of HARQ-IDs which are pre-configured by the base station.
 3. The method according to claim 1, wherein selecting the at least one HARQ-ID for the at least one PUSCH includes: selecting a plurality of HARQ-IDs for a plurality of uplink channels to be transmitted according to the UL configuration.
 4. The method according to claim 3, wherein each of the plurality of uplink channels includes a corresponding HARQ-ID.
 5. The method according to claim 4, wherein each of the plurality of uplink channels further includes a redundancy version (RV) and a new data indicator (NDI).
 6. A device comprising: a processor; and a memory operatively coupled with the processor and configured to store instructions that, when executed by the processor, cause the device to perform functions comprising: receiving, from a base station, an UL configuration for configure uplink (UL) transmission without dynamic UL grant in which the device performs UL transmission in accordance with the UL configuration, the UL configuration including a periodicity for the UL transmission without UL grant and a number of allocated slots in the periodicity; selecting at least one hybrid automatic repeat request process identifier (HARQ-ID) for at least one UL channel to be transmitted according to the UL configuration; perform listen before talk (LBT) to check that the unlicensed band is idle in the allocated slots; and transmitting, to the bases station, the at least one uplink channel in at least one slot of the allocated slots based on the unlicensed band being idle, wherein the at least one uplink channel includes the at least one selected HARQ-ID.
 7. The device according to claim 6, wherein the at least one HARQ-ID for the at least one uplink channel is selected among a plurality of HARQ-IDs which are pre-configured by the base station.
 8. The device according to claim 6, wherein selecting the at least one HARQ-ID for the at least one PUSCH includes: selecting a plurality of HARQ-IDs for a plurality of uplink channels to be transmitted according to the UL configuration.
 9. The device according to claim 8, wherein each of the plurality of uplink channels includes a corresponding HARQ-ID.
 10. The device according to claim 9, wherein each of the plurality of uplink channels further includes a redundancy version (RV) and a new data indicator (NDI).
 11. A method performed by a base station and comprising: transmitting, to a wireless device operating in an unlicensed band, an UL configuration for configure UL transmission without dynamic UL grant in which the wireless device performs UL transmission in accordance with the UL configuration, the UL configuration including a periodicity for the UL transmission without UL grant and a number of allocated slots in the periodicity; and receiving, from the wireless device, at least one uplink channel in at least one slot of the allocated slots, wherein the at least one uplink channel includes at least one hybrid automatic repeat request process identifier (HARQ-ID) which is selected by the wireless device.
 12. The method according to claim 11, wherein the at least one HARQ-ID for the at least one uplink channel is selected among a plurality of HARQ-IDs which are pre-configured by the base station.
 13. Abase station comprising: a processor; and a memory operatively coupled with the processor and configured to store instructions that, when executed by the processor, cause the base station to perform functions comprising: transmitting, to a wireless device operating in an unlicensed band, an UL configuration for configure UL transmission without dynamic UL grant in which the wireless device performs UL transmission in accordance with the UL configuration, the UL configuration including a periodicity for the UL transmission without UL grant and a number of allocated slots in the periodicity; and receiving, from the wireless device, at least one uplink channel in at least one slot of the allocated slots, wherein the at least one uplink channel includes at least one hybrid automatic repeat request process identifier (HARQ-ID) which is selected by the wireless device.
 14. The base station according to claim 13, wherein the at least one HARQ-ID for the at least one uplink channel is selected among a plurality of HARQ-IDs which are pre-configured by the base station. 